JPS62190725A - Alignment system by means of double diffraction grating - Google Patents

Abstract

PURPOSE:To enhance the detecting accuracy of an alignment system by forming diffraction gratings of the same phase at the same pitch on a mask and a wafer, introducing coherent light or metamonochromatic light to the gratings, adding the same diffracted lights of the same order as the reflected lights generated from the grating groups of sets, and adjusting the gap between the mask and the wafer and aligning them by the variation in the added value. CONSTITUTION:The pitch of diffraction gratings 104 is the same as that of diffraction gratings 105 of a wafer 102. A laser light from a laser emitting unit 106 is reflected by a beam splitter 107, and incident from above a mask 101 perpendicularly. Then, positively reflected light (0 order light) 108 passes the beam splitter 107 to be detected by a detector 109. The primary diffracted light 110 and + primarily diffracted light 111 are detected by detectors 112, 113. The outputs of the detectors 109, 112, 113 are added by an adder 114, and used as an alignment signal. Since the output waveform W2 of the detector 112 is added with the output waveform W1 of the detector 109 even if it is varied due to a gap (g), the influence of the gap (g) to the waveform W3 of the added result is alleviated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for aligning a pattern on a wafer and a mask pattern using a double diffraction grating in a printing apparatus for semiconductors and the like.

(Prior art) Traditionally, semiconductors, etc. have been printed using a system in which a double diffraction grating is used in an apparatus to adjust the gap and position between the pattern on the wafer and the mask pattern. As a combination method, for example, JP-A-80-77423@publication and JP-A-56-122
There is an alignment method described in Japanese Patent No. 128.

The alignment method described in Japanese Patent Application Laid-Open No. 80-774238 is such that coherent light or monochromatic light is perpendicularly incident on a first diffraction grating provided on a mask and a second diffraction grating provided on a wafer. This is a method in which the intensities of all the diffracted lights of the same order that are diffracted in directions symmetrical to the light are added, and the gap and relative displacement between the mask and the wafer are detected and aligned based on changes in the added intensities.

This method will be explained below with reference to FIGS. 8 and 9.

In FIG. 8, reference numeral 1 is a wafer, 2 is a diffraction grating provided on the wafer, 3 is a mask, 4 is a diffraction grating provided on the mask 3, 5 is a laser light source, 6.7 is a detector, 8 is an adder, 9 is a mask fine adjustment stage, and 10 is a wafer fine adjustment stage.

In this configuration, coherent light emitted from the laser light source 5 enters the diffraction grating 4 on the mask 3. mask 3
The light diffracted by the diffraction grating 4 is transmitted to the fine adjustment stage 10.
It is reflected by the diffraction grating 2 of the wafer 1 held above and passes through the diffraction grating 4 on the mask 3 again. Of the light diffracted by the diffraction grating 2.4 of these wafer 1 and mask 3, +1
A detector 6.7 receives only the second and eleventh-order diffracted lights, and converts the light intensity into an electrical signal.

Next, the adder 8 adds the +1st-order diffracted light intensity T++ and the 11th-order diffracted light intensity I-+ to obtain ΣI-1++ +I-+.

As shown in FIG. 9, the change in the added intensity ΣI with respect to the gap Z is caused by a signal having a peak at each P2/λ and the influence of reflection on the back surface of the mask 3, that is, the surface on which the diffraction grating 4 is provided. It is shown as a signal in which a signal having a period of 2 is superimposed.

A signal with a peak at P2/λ, 2P2/λ,...
This signal is obtained under ideal conditions with zero reflection on the back surface of the mask, and by processing this signal, which changes at λ/2, using an integrator or the like, the envelope can be obtained. Therefore, by adjusting the gap Z to its maximum value while monitoring this envelope, P2/λ
, 2P2/λ, . . .

Therefore, this alignment method has the advantage of not being affected by the resist or by the gap.

Furthermore, Japanese Patent Laid-Open No. 56-122128 discloses that one of the alignment patterns formed on the wafer and the mask has a predetermined pitch, and the other pattern has a pattern that is repeated at the same pitch. first of half
a set of patterns, a pitch of this first pattern, and 17
By comprising a second pattern set with a phase shift of two pitches and a second pattern having the same pitch interval as the first pattern, alignment using a "0" potential is possible.

This method will be explained with reference to FIGS. 10 to 12.

In FIG. 10, reference numeral 11 indicates a lens for pattern projection, 12 a mask, 13 a wafer, and 14, 15, and 16 the directions of light for pattern printing. 17 is a laser light source, 18 is a locus of the emitted laser beam, 19 is a specularly reflected locus of this laser beam, 20 is a locus of diffusely reflected light from a pattern on a wafer, and 21 is a pattern on a wafer that is a lens. 11 and projected onto the mask 12. In this configuration, the alignment pattern on the wafer 13 is irradiated with laser light from the laser light source 17, and the intensity of the light is detected by the detectors 22A and 22B.

Although only one is shown in FIG. 10, two are actually arranged along the pattern.

FIG. 11 shows an example of alignment patterns formed on a wafer, in which 23 is a pattern on a mask, 2
4 is a pattern on the wafer, and the intervals between these patterns are the same. Note that the pattern 23 on the mask and the pattern 24 on the wafer may be reversed.

In the figure, 25 is a reflective portion, and 26 is a non-reflective portion. In the pattern 23 part on the mask, there are windows 27 and 28 that allow a large number of light to pass through and non-transparent parts at the same intervals, and A,
They are formed with a 1/2 pitch phase shift in the portion B. Then, the reflective portion 25 of the pattern 24 on the wafer 13
The light emitted from the mask passes through a window 27 or 28 on the mask, and the light passing through the window 27 is detected by the detector 22A, and the light passing through the window 28 is detected by the detector 22B.

In the state shown in FIG. 11, the pattern on the wafer and the pattern on the mask perfectly match in the range A and completely deviate from each other in the range B, so the output of the detector 22A is maximum, and the output of the detector 22B is the maximum. has the lowest output. Next, as the wafer is moved in the direction of arrow
Since the overlap between the window 28 and the reflection part 25 gradually decreases, the output of the detector 22A gradually decreases, and in the range B, the overlap between the window 28 and the reflection part 25 gradually increases, so the detection The output of the device 22B gradually increases. When the wafer moves by 172 pitches in the direction of arrow X,
The outputs of the detectors 22A, 22B are completely reversed, and the above relationship is restored after one pitch movement.

FIG. 12(a) shows the relationship between the output voltages of the detectors 22A and 22B and the amount of wafer movement in the direction of arrow X, where the horizontal axis shows the amount of wafer movement and the vertical axis shows the amount of wafer movement. Indicates the output voltage of the device. In the figure, W1 indicates the output voltage of the detector element 22A, and W2 indicates the output voltage of the detector 22B.

In the figure, points a and b are when the wafer and mask are in the positional relationship shown in FIG. 11, and as the wafer moves in the direction of arrow X in FIG. It changes in the direction shown by arrow X in Fig. 12(a). Point C is the output voltage of each detector when the wafer moves by 1/2 pitch.

Next, the curve indicated by W3 in FIG.
This is a curve obtained by subtracting the output voltage of A and the output voltage of the detector 22B using a subtracter. As is clear from the figure, this curve swings positive and negative around O. Here, the point indicated by n is the point when the output voltages of the detectors 22A and 228 are equal, that is, when the wafer has moved by 172 pitches in the X direction.

Therefore, if this state is set as a state in which alignment has been achieved, the mask and wafer can be aligned with reference to the "0" potential shown in FIG. 12(b).

By the way, in general, there is a slight difference in reflectance depending on the position of the reflective part on the wafer, and it is also possible that there is a deviation in the direction perpendicular to the pattern arrangement direction, and the light intensity of the laser light source also changes over time. However, in this method, the changes in part A and part B cancel each other out, so S/
It has the advantage of having a good N ratio and being unaffected by changes in the object and incident light. This method also has the advantage of not being affected by the gap between the mask and the wafer because it uses only reflected light.

(Problems to be Solved by the Invention) However, the alignment method described in JP-A-60-77423 has a poor S/N ratio of the detection signal, and is sensitive to changes in the intensity of the object and incident light. However, if the gap is not adjusted to more than ±1 μm, the signal detection level becomes extremely poor and positioning becomes difficult.

Furthermore, the positioning method described in JP-A-56-122128 has a detection accuracy of ±0.02 to ±0.03 μm.
This method is not very good, and has the drawback of being easily affected by the resist, and also has the drawback of not being able to detect gaps.

The present invention has been made to solve these conventional drawbacks, and takes advantage of the fact that each of the above-mentioned drawbacks of each alignment method is an advantage of the other, and by combining the two methods, the drawbacks of the prior art can be overcome. The purpose is to provide an alignment method that does not require

(Means for solving problems) The alignment method of the present invention includes the following methods.

(b) Diffraction gratings with the same pitch and the same phase are formed on the mask and the wafer, and cohesive 12 = left light or quasi-monochromatic light is incident on these diffraction gratings, and the reflected light generated by the group of diffraction gratings of each phase is reflected. A method in which the difference between the mask and the wafer is adjusted and the gap between the mask and the wafer is adjusted based on changes in the addition value.

(b) A diffraction grating with a predetermined pitch is formed on either the mask or the wafer, and a first diffraction grating group that is repeated at the same pitch on the other;
forming a diffraction grating composed of a second diffraction grating group whose phase is shifted by approximately 1/2 pitch from the pitch of the diffraction grating group and whose pitch interval is the same as that of the first diffraction grating group;
Coherent light or quasi-monochromatic light is incident on each set consisting of one diffraction grating and each diffraction grating group on the other side, and the diffracted lights of the same order generated in each set of diffraction gratings are added for each set, and then A method that adjusts the gap and aligns the mask and wafer by determining the difference between each set of results of addition processing of diffracted light.

(c) A diffraction grating with a predetermined pitch is formed on either the mask or the wafer, and a first diffraction grating group repeated at the same pitch is formed on the other one, and this first diffraction A second diffraction grating group whose phase is shifted by approximately 1/2 pitch from the pitch of the grating group and whose pitch interval is the same as that of the first diffraction grating group is formed, and one diffraction grating Coherent light or quasi-monochromatic light is incident on each group of diffraction gratings, and the diffracted light of the same order as the reflected light generated by each group of diffraction gratings is added for each group, and then the reflected light is A method that adjusts the gap and aligns the mask and wafer by calculating the difference between each set of results of addition processing of light and diffracted light.

(d) forming a diffraction grating with a predetermined pitch on either the mask or the wafer; a first diffraction grating group repeated at the same pitch on the other;
forming a diffraction grating composed of a second diffraction grating group whose phase is shifted from the pitch of the diffraction grating group by 1/2 pitch and whose pitch interval is the same as that of the first diffraction grating group;
Coherent light or quasi-monochromatic light is incident on each set consisting of one diffraction grating and each group of diffraction gratings on the other side, and the diffracted light of the same order generated by each set of diffraction gratings is added for each phase and roughly A method of adjusting the gap and positioning between the mask and the wafer by determining the difference between each set of reflected light and the difference between each set of the results of addition processing of the diffracted light.

(Function) According to the method (a), in addition to obtaining the advantages of the positioning method described in Japanese Patent Laid-Open No. 60-77423@, the influence of the gap can be alleviated.

In addition, the method described in (mouth) has the advantages of the method described in JP-A-56-122128 except that it is affected by gaps, and also improves the detection accuracy, which was considered a drawback with this method. This eliminates the influence of the resist and also makes it possible to detect gaps.

According to the method (c), it is possible to obtain both the advantages of the method described in JP-A-60-77423 and the method described in JP-A-56-122128. According to the method (2), in addition to obtaining the advantages of the method (c), the difference between each set of reflected light is used for rough adjustment, and the result of each set obtained by adding the diffracted lights of the same order. The difference can be used for fine adjustment, and it becomes possible to perform quick and highly accurate positioning.

(Embodiment) FIG. 1 is a configuration diagram showing an embodiment of the alignment method according to the present invention.

In FIG. 1, reference numeral 101 indicates an original mask of a pattern to be printed, and reference numeral 102 indicates a wafer on which the pattern will be printed. 103 is the pitch of the diffraction grating on the mask, and is set to P=about 3 μm.

The pitch of the diffraction gratings 104 on the mask 101 is the same as the pitch of the diffraction gratings 105 on the wafer 102.

The diffraction grating 104 on the mask 101 is made of a non-reflective, non-transmissive film, so that it does not reflect the incident light from the upper part of the mask 101 and does not transmit the incident light.
A portion of the mask 101 where there is no pattern of the diffraction grating 1O4 is a transparent portion.

The diffraction grating 105 on the wafer 102 is made of a non-reflective film,
A portion of the diffraction grating 105 without a pattern is a reflective portion. Therefore, when viewing these diffraction gratings from the top of the mask, as the relative positional relationship between the mask 101 and the wafer 102 is shifted, depending on the position, the diffraction gratings on the wafer 102 can be seen from the window (transparent part) where the diffraction grating of the mask 101 has no pattern. Reflective areas (bright areas) and non-reflective areas (dark areas) are observed alternately, and when aligned, the mask 10
Only the reflected portion on the wafer 102 is visible through the window of the first diffraction grating.

In FIG. 1, 106 is a laser emitting device, for example, and the laser beam is reflected by a beam splitter 107 and is made to enter perpendicularly from the upper part of the mask 101.

Due to this laser beam, specularly reflected light (0th order light) 108 is transmitted through a beam splitter 107 and detected by a detector 109. In addition, −1st order diffracted light 110 and +1st order diffracted light 11
1 are detected by detectors 112 and 113, respectively. The outputs of the detectors 109, 112, and 113 are summed by a stressor 114 and used as a positioning signal.

Next, the waveforms of each detector will be explained with reference to FIG.

FIG. 2(a) shows the output waveform W1 of the detector 109, and FIG. 2(b) shows the output waveform W2 of the detectors 112 and 113.

The waveform in Figure 2(b) has exactly the same relationship as the waveform in Figure 2(a), but in Figure 2(a) it is always at ten potentials due to reflection on the resist surface. On the other hand, in the case of FIG. 2(b), since the specularly reflected light is not detected, it is unrelated to the reflection on the resist surface, and therefore the minimum value of the waveform is the #011 potential.

FIG. 2(C) shows a waveform W3 obtained by modifying the waveforms shown in FIGS. 2(a) and 2(b) using the tampering device 114.

Here, since FIG. 2(a) is specularly reflected light, the waveform W1 is not affected by the gap between the mask 101 and the wafer 102, and the width of the waveform W1 is determined by the beam splitter 107 before addition by the adder 114. It is possible to add the specularly reflected light after changing its transmittance or electrically attenuating it, and it is possible to change the addition level of the specularly reflected light to an appropriate level depending on the state of the resist on the wafer 102. .

On the other hand, the waveform W2 in FIG. 2(b) is not affected by the resist, but on the contrary, the gap q between the mask 101 and the wafer 102
It has the drawback that it is easily affected by fluctuations in , and it is difficult to obtain a normal output waveform unless the gap q is within 1 μm.

Therefore, even if the waveform W2 in FIG. 2(b) changes due to the gap Q, the waveform in FIG. 2(a) is added to the adder 114 as a component unrelated to the gap q, The influence of the gap q on the waveform W3 in C) is alleviated.

In addition, in this embodiment, one method of alignment is as follows:
Rapid and highly accurate positioning is achieved by increasing the specularly reflected light component during rough adjustment at the beginning of positioning, and conversely increasing the ratio of diffraction components at the fine adjustment stage near the end of positioning. becomes possible.

Equation (1) is generally known as an equation showing the relationship between the gap q in FIG. 1, the wavelength of the laser beam, and the pitch P of the diffraction grating.

q-P2/λ (1) The value of the gap q in this example and the value of the wavelength of the 1e-Ne laser (wavelength 0.6328 μm) are expressed in equation (1). Substituting, q-(3μm > 2/ 0.6328μm=14.2
2 μm, and it can be seen that the intensity of the ±1st-order diffracted light reaches its maximum at q=14.22 μm.

FIG. 3 is a configuration diagram showing another embodiment of the present invention.

The structure and pitch of the mask 101, square box 02, and diffraction grating in FIG. 3 are the same as in the embodiment shown in FIG.
It is divided into two lattice groups: and B.

Further, the pitch of the diffraction gratings 105 on the wafer 102 is the same as the pitch of the diffraction gratings 104 on the mask 101,
Two sets of diffraction gratings 105 on the wafer 102 are also provided in the arrangement direction corresponding to the diffraction grating groups A and B of the mask 101. As will be described later, these diffraction gratings A and B are formed so that when they are aligned, the correspondence relationship between the diffraction grating group A and the diffraction grating group B is shifted by 172 pitches from each other. ing.

When looking at these diffraction grating groups A1B from above the mask 101, as shown in FIG.
By adjusting the positional relationship between the two, it is possible to move from the window (transmissive part) X of the grating of the mask 101 to the reflective part (
A bright part) Y+ and a non-reflective part (dark part) Y2 are observed, but in the aligned state, the arrangement of the reflective part Y1 and the non-reflective part Y2 in the diffraction grating group B is different. It's the other way around.

That is, when only the reflective portion Y1 is visible in the diffraction grating group A, only the non-reflective portion Y2 appears in the diffraction grating group B, and conversely, when only the non-reflective portion Y2 is visible in the diffraction grating group A, the diffraction grating In group B, the reflective part Y
The correspondence between the diffraction gratings 105 and 106 is shifted by 172 pitches in the diffraction grating group B so that only 1 appears.

In FIG. 3, the laser beam emitted from the laser emitting device 106 is transmitted to beam splitters 107a and 107b.
, and enters vertically from the upper part of the mask 101 .

This laser beam causes specularly reflected lights 108a and 108b to be transmitted through beam splitters 107a and 107b, respectively, and detected by detectors 109a and 109b. In addition, −1st-order diffracted light 110a, 110b and +1st-order diffracted light 111a
, 111b are the detectors 112a, 112b, 11, respectively.
3a and 113b. The outputs of these detectors are obtained by adding the outputs of 109a, 112a and 1113a of diffraction grating group A in an adder 114a, and the outputs of 109a and 112a of diffraction grating group B are
The outputs of b1112b and b113b are added by an adder 114b. The outputs of the adder 114a and the adder 114b are subtracted by a subtracter 115 and used as a positioning signal.

Next, the waveforms of each detector will be explained with reference to FIG.

FIG. 5 (a> is the output waveform W1a of the detector 109a,
It shows the output waveform W1b of the detector 109b. As shown in FIG. 5(a), the output waveforms W1a and W'lb have a phase shift of 1/2 pitch, and the wafer 10
Output waveforms W1a and W when the diffraction grating position of 2 is moved
The direction of increase/decrease in lb is completely opposite.

FIG. 5(b) shows the output waveform W2a of the detectors 112a and 113a (7) and the output waveform W2b of the detectors 112b and 1'13b (7).

The waveform in FIG. 5(b) has exactly the same relationship as the waveform in FIG. 5(a), but in the case of FIG. 5(b), the specularly reflected light is not detected, so the resist surface The minimum value of the waveform is the "0" potential.

FIG. 5(C) shows how the solid line waveforms (each output of the diffraction grating group A) shown in FIGS. 5(a) and 5(b) are transferred to the adder 114a.
and the broken line waveforms (each output of the diffraction grating group B) shown in FIGS. 5(a) and 5(b) are added by the adder 114b.
The waveform W3ab is the result of subtracting the output of the adder 114b from the output of the adder 114b.

As shown in FIG. 5(C), the output of the subtracter 115 is 10 V.
The positioning point can be set at the potential "Ot+".

In this embodiment, alignment is performed at the potential "O", so even if the amplitude of the waveforms shown in FIGS. In the example, the S/N ratio is significantly improved.

Furthermore, since the waveform in FIG. 5(a) is positive [=l ahead, it is not affected by the gap q between the mask 101 and the wafer 102, and the amplitudes of the waveforms W1a and Wlb are added by adders 114a and 114b. Beam splitter 107 before
It is possible to change the transmittances of a and 107b or to add them after electrically attenuating them, and it is also possible to change the addition level of specularly reflected light depending on the state of the resist on the wafer 102. .

The waveforms W2a and W2b in FIG. 5(b) are not affected by the resist, but are easily affected by fluctuations in the gap q between the mask 101 and the wafer 102, and if the gap Ω is not within 1 μm, the output waveforms are normal. The disadvantage is that it is difficult to obtain.

Therefore, the waveform in FIG. 3(b) varies depending on the gap q, but since the adders 114a and 114b add the waveform due to regular reflection in FIG. 3(a) as a component unrelated to the gap Ω, The effect of gap q is alleviated. Furthermore, the influence of the gap can also be eliminated by detecting alignment at the potential "0" in FIG. 3(C).

In this embodiment, as in the embodiment shown in Fig. 1, the rough adjustment at the beginning of alignment increases the specularly reflected light component, and in the fine adjustment stage near the end of alignment, the ratio of the diffraction component is conversely increased. In most cases, it is possible to perform quick and highly accurate positioning.

Furthermore, as explained in the embodiment of FIG.
When an e-laser (wavelength: 0.6328 am) is used, the intensity of the ±1st-order diffracted light reaches its maximum at Q=14.2'2 μm.

FIG. 6 is a diagram showing the configuration of still another embodiment of the present invention. In the following description of the embodiment, the same parts as in FIG. 3 are denoted by the same reference numerals, and redundant description will be omitted.

This embodiment has the same configuration as the embodiment shown in Figure 3 except that the detectors 109a and 109b are omitted. Therefore, in this embodiment, the gap adjustment and alignment between the mask 101 and the wafer 102 are performed using the ±1st-order diffracted light 110.
This is performed only in a, 111a, 11ob, and 111b.

In this embodiment as well, positioning is performed by detecting the "O" potential, so there is an advantage that the S/N ratio is good and there is less influence from gaps than in the conventional method.

FIG. 7 is a diagram roughly showing the configuration of another embodiment of the present invention. In this embodiment, the outputs of the detectors 109a and 109b are subtracted by a subtractor 116a, and the ±1st order diffracted light 11a,
111a and 110b.

Brighteners 114a are each added with only 111b.

The output of 114b is subtracted by a subtracter 116b, the detection and calculation of specular reflection light and the detection and calculation of ±1st-order diffracted light are performed separately, and the calculation result of specular reflection light is used for rough adjustment. However, it is configured to use the derivation results of the ±1st-order diffracted light for fine adjustment.

In addition to having the advantages of the method shown in FIG. 3, this embodiment increases the specularly reflected light component in the rough adjustment at the beginning of alignment, and
In the fine adjustment stage near the end of alignment, on the contrary, the ratio of the diffraction component is increased, making it possible to perform rapid and highly accurate alignment.

(Effects of the Invention) As explained above, in the present invention, while the regularly reflected light of the detection light incident perpendicularly to the mask surface is not affected by the gap, it is affected by the resist, and the diffracted light is affected by the resist. Although high detection accuracy can be expected without being affected by this, it is easy to be affected by fluctuations in the gap between the mask and wafer, and this is combined with "0" potential detection technology by dividing the diffraction grating. Since it is used, the following effects can be achieved depending on the implementation.

(1) Detection accuracy is good and can be expected to be around ±0.01 μm.

(2) Less affected by resist.

(3) The gap between the mask and the wafer can be detected.

(4) The S/N ratio of the detection signal is good and is not easily affected by the mask, wafer, or intensity of incident light.

(5) Horizontal alignment can be performed independently without being affected by gaps.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of an embodiment of the present invention, Figures 2 (a), (
b) and (C) are waveform diagrams showing waveforms detected by each detector shown in Fig. 1, Fig. 3 is a configuration diagram showing another embodiment of the present invention, and Fig. 4 is this embodiment. 5A, 5B, and 5C are plan views showing the alignment of the orthogonal gratings formed on the mask and the wafer in FIG. FIG. 6 and FIG. 7 are respectively diagrams showing the configuration of further embodiments of the present invention, and FIG. 8 is a configuration diagram of a conventional positioning method using a diffraction grating. FIG. 9 is a block diagram of another conventional alignment method, FIG. 10 is a block diagram of a mask and wafer alignment method which is also applied to the present invention, and FIG. 11 is a diagram showing an example of a conventional repeating pattern. , FIGS. 12(a) and 12(b) are waveform diagrams showing waveforms detected by each detector of the embodiment shown in FIG. 10. 101・・・・・・・・・Mask 102・・・・・・
...Wafer 103...
・Diffraction grating pitch 104.105...
. . . Diffraction grating 106 . . . Laser emitting device 107.107a, 107b . . . Beam splitter 108.1
08a, 108b ...... Specular reflected light (0th order light) 109.
109a, 109b, 112.112a, 112b, 1
13.113a. 113b......Detector 110.11
0a, 110b ...... - 1st order diffracted light 111.111
a, 111b ・・・・・・・・・・・・+1st order diffracted light 114.114
a, 114b Brighteners WLW2, W3, Wla, Wl b. W2a, W2b, W3ab.・・・・・・・・・・・・Output waveform 115・・・・・・・・・・・・・・・Subtractor applicant
Satoshi Suyama, Patent Attorney, Tokyo Electron Co., Ltd. - 8 To Asahi@& Figure 10 Figure 12 Figure 11

Claims (7)

[Claims] (1) A diffraction grating provided on a mask and a diffraction grating provided on a wafer are overlapped with a certain gap, and coherent light or quasi-monochromatic light is incident on these diffraction gratings, and each set of diffraction gratings In the alignment method, which detects the relative displacement of the mask and wafer and aligns them based on changes in the intensity of the reflected light or diffracted light, the reflected light and the diffracted light of the same order are added together, and the change in the added value is Therefore, this is an alignment method using a double diffraction grating, which is characterized by performing gap adjustment and alignment between the mask and the wafer. (2) The positioning method using a double diffraction grating according to claim 1, wherein the intensity of the reflected light is appropriately attenuated and added. (3) The first and second diffraction gratings provided on the mask and the third and fourth diffraction gratings provided on the wafer are overlapped with a certain gap, and each of these first to fourth diffraction gratings In the alignment method, the relative displacement of the mask and the wafer is detected and aligned based on a change in the intensity of reflected light or diffracted light generated by each of the sets of diffraction gratings by inputting coherent light or quasi-monochromatic light to the grating group. The correspondence relationship between the first diffraction grating and the third diffraction grating set and the correspondence relationship between the second diffraction grating and the fourth diffraction grating set are approximately 1/2 of each other.
Gap adjustment and alignment between the mask and wafer are performed by adding the diffracted lights of the same order to each set with a pitch-shifted positional relationship, and determining the difference between each set of the results of the addition process of the diffracted lights. An alignment method using a double diffraction grating that is characterized by performing the following. (4) The first and second diffraction gratings provided on the mask and the third and fourth diffraction gratings provided on the wafer are overlapped with a certain gap between each of these first to fourth diffraction gratings. In the alignment method, the relative displacement of the mask and the wafer is detected and aligned based on a change in the intensity of reflected light or diffracted light generated by each of the sets of diffraction gratings by inputting coherent light or quasi-monochromatic light to the grating group. The correspondence relationship between the first diffraction grating and the third diffraction grating set and the correspondence relationship between the second diffraction grating and the fourth diffraction grating set are approximately 1/2 of each other.
Addition processing is performed for each set of diffracted light of the same order as the reflected light with a positional relationship with a pitch shift, and the difference between each set of the results of the addition processing is determined to adjust the gap and position between the mask and the wafer. An alignment method using a double diffraction grating that is characterized by performing the following. (5) The positioning method using a double diffraction grating according to claim 4, wherein the intensity of the reflected light is appropriately attenuated and added. (6) The first and second diffraction gratings provided on the mask and the third and fourth diffraction gratings provided on the wafer are overlapped with a certain gap between each of these first to fourth diffraction gratings. A positioning method in which coherent light or quasi-monochromatic light is incident on the wafer, and the relative displacement of the mask and wafer is detected and aligned based on changes in the intensity of the reflected light or diffracted light generated by each set of diffraction gratings. In the above, the correspondence relationship between the first diffraction grating and the third diffraction grating set and the correspondence relationship between the second diffraction grating and the fourth diffraction grating set are approximately 1/2 of each other.
The positional relationship is shifted by the pitch, and the diffracted lights of the same order are added for each set, and the difference between each set of reflected light and the difference between each set of the results of the addition processing of the diffracted lights are calculated to form a mask. An alignment method using a double diffraction grating that is characterized by adjusting the gap between wafers and aligning them. (7) The difference between each set of reflected light is used for rough adjustment, and the difference between the results of each set of addition processed diffracted lights of the same order is used for fine adjustment. Alignment method using double diffraction grating.